Process of producing hydrogen



Patented June 7, 1938 UNITED STATES PATENT OFFICE mesne assignments, toE. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation ofDelaware No Drawing. Original Serial No.

2 Claims.

This invention relates to a method of manufacturing hydrogen from.gaseous mixtures of steam and hydrocarbons with the aid of a catalyst,and particularly to the production of hydrogen of relatively low carbonmonoxide content. This application is a division of my copendingapplication Serial No. 118,600, filed June 25, 1926.

Because of the rapidly increasing consumption of hydrogen, particularlyin such processes as the hydrogenation of oils and the synthesis ofammonia, the development of an abundant supply of hydrogen at relativelylow cost is of great economic importance. Hydrogen has been producedheretofore principally by electrolysis of water, but except where waterpower is. abundant the cost of recovering hydrogen by electrolysis istoo great to permit the economic use thereof for many purposes.

It is the object of the present invention to provide a simple andeffective process operating at a comparatively low temperature for theproduction of hydrogen by the catalytic reaction of steam andhydrocarbons, the process being adapted particularly for use inconverting the saturated paraffin hydrocarbons such as methane, ethane,propane and the like. These are the principal hydrocarbon constituentsof natural gas, cokeoven gas and waste'gas from oil cracking processesand an abundant supply thereof is available.

A further object of the invention is to provide a process ofmanufacturing hydrogen of relatively low carbon monoxide content, suchhydrogen being particularly desirable for use in the hydrogenation ofoils or the synthesis of ammonia in which the catalysts are poisoned bythe presence of carbon monoxide in the hydrogen used.

The production of hydrogen by reaction between steam and hydrocarbon hasbeen suggested heretofore, notably in United States Patents No. 314,342,No. 417,068 and No. 1,128,804, but so far as I am aware none oftheprocesses described has achieved any commercial importance. They arenot adapted in any event for satisfactory use in the production ofhydrogen from hydrocarbons and of a quality suitable for use directly inthe hydrogenation of oils and the production of synthetic ammonia.

There are various reasons for the inoperativeness or nonadaptability ofthe processes described in the patents mentioned. The process proposedin U. S. Patent No. 314,342 consists in passing steam and hydrocarbonsover metallic iron, manganese, copper, lead, tin or zinc, or oxides ofapplication June 25, 1926, 118,600. Divided and this application May 25,1928, Serial these metals in situ at temperatures from 350 to 400 C. fornickel and 400 to 450 C for cbalt. The primary difliculty with thisprocess is that neither nickel nor cobalt reduced from the chlorides asdescribed will effect the conversion of hydrocarbons into hydrogen inthe presence of steam at the temperatures described in the patent or athigher temperatures up to or above 600 C. It is evident that theconversion obtained in the practice of this process depends solely uponthe presence of carbon monoxide, the process being useless for theconversion of hydrocarbons. The process of United States Patent No.1,128,804 depends upon the use of high temperatures above 700 C. and theuse of a nickel catalyst. While it is possible at such temperatures toconvert hydrocarbons into hydrogen, the process is in fact useless forthe present purposes because the product contains always a largeproportion of carbon monoxide.

I have found that in the manufacture of hydrogen from hydrocarbons andsteam by contact with a catalyst it is desirable to maintaintemperatures materially below 700 C. At the latter temperature catalysts(except such as .are very refractory and consequently comparativelyinactive) ordinarily sufier considerable deterioration by sintering orother change in physical form. Furthermore, at temperatures of 700 C. orhigher the conversion of the hydrocarbons will result in a carbonmonoxide content in the resultant gaseous mixture of or more unless theproportion of steam employed is in such excess as to render the processvery costly. The reason for this condition is apparent from aconsidera-' tion of the following reactions:

Ihave found that at temperatures above 600 C. there is a tendency tofollow the first and least desirableof these reactions, whereas attemperaturesv of 600 C. or below the second reaction prevails with theproduction, therefore, of the minimum proportion of carbon monoxidelNickel alone even with the exclusion of chlorlne and other catalystpoisons is not very active for the production of hydrogen by a reactionbetween steam and hydrocarbons at temperatures below 700 C. I havediscovered, however, that by the addition of suitable substancesreferred to hereinafter as promoters the catalytic behavior of nickel inthis reaction can be improved to the extent that the conversion ofhydrocarbons into hydrogen becomes practicable at temperaturesmaterially below 700 C. The term promoter" is employed herein todesignate one of the materials of the following group,-

cerium oxide, yttrium oxide, thorium oxide, zirconium oxide,molybdenum-oxide, vanadium oxide, tungsten oxide, uranium oxide,titanium oxide, glucinum oxide, chromium oxide, aluminum 1 duce resultsbetter oxide, manganese oxide, silicon oxide, tantalumoxide, boronoxide, zinc oxide, cadmium oxide, potassium oxide and calcium oxide.While the addition of promoters to nickel catalysts is especiallyadvantageous since it permits the production of hydrogen fromhydrocarbons and steam at temperatures even below 700 C., ness of suchpromoted nickel catalysts is not, limited to these temperatures. Theoperation can be conducted, therefore, at-higher temperatures providedit be carried out in such a way as to prevent the production ofexcessive proportions of carbon monoxide, for example, by the use oflarge quantities of steam; or if, on the other hand, the presence ofcarbon monoxide is not detrimental to the usefulness of the gaseousproduct. I have also discovered that more than one promoter may be addedto nickel to prothan those obtained with the use of 'a single promoter.Thus, the combinationof cerium and aluminum oxides with nickel producesa more effective catalyst than that resulting from the addition of oneof these oxides v alone to nickel. The term promoter as used in theclaims hereof includes, therefore, one or more of the elementshereinbefore mentioned as suitable for the purpose.

- Another feature of my invention consists in the discovery that the.promoting-action of a given oxide for the hydrocarbon conversioncatalyst is considerably improved if the promoter is combined with thecatalyst in the form of a chemical compound. Thus, a compound of nickeland chromium oxide is a more activecatalyst than a mixture of nickel andchromium oxide. Similarly, nickel borate is a-better catalyst than amixture of nickel and boron oxide.

I have 'also discovered that the absence of even relatively smallproportions of certain substances from the catalyst and the reactinggases is essential to the most eiiicient conversion of greatly decreaseor even completely inhibit the activity of nickel catalysts for thispurpose.

Among such substances are the halogens, such as chlorine, and compoundsof sulphur. It is,

therefore, advisable to avoid the presence of these and other catalystpoisons, for instance, by using salts other than the chlorides in preparing the catalytic materials and by employing gases which are free fromcompounds of sulphur.

The following examples will serve to indicate the preferred procedure incarrying out'the invention, it being understood, however, that the theuseful- I such as nickel chromate invention is not limited to thedetails of the operation as herein described.

Example 1.--Crush pumice stone and screen to 8-14 mesh. Wash withboiling hydrochloric acid until free from iron and then with boilingdistilled water until free from chlorides. After drying at 200 C. stirparts at that temperasupply a mixture of 10 volumes of steam and 1volume of methane, previously freed from contact poisons, by passageover hot copper and through activated charcoal, for example. Maintain atemperature of 500 C. and a space velocity of 250, based on methane.(The space velocity is the volume of gas flowing under standardconditions of temperature and pressure per unit volume of catalyst perhour.) The issuing gases should contain 76% to 79% of hydrogen, 1% to 4%of methane, 18% to 19% of carbon dioxide and less than 2% of carbonmonoxide (on a dry basis). Throughout the operation all con tact poisonsshould be excluded.

Example 2.--A nickel alumina catalyst can be prepared by substitutingfor the solution of nickel nitrate and cerium nitrate of Example 1 asolution of 50 parts of nickel nitrate and 7.5 parts of aluminum nitratein 70 parts of distilled water.

Example 3.--A nickel alumina catalyst can be prepared also asfollows:-Heat a 6% solution of nickel nitrate in distilled watercontaining 15 parts of aluminum nitrate for each 100 parts of nickelnitrate to 40 C. Add a 6% solution of potassium hydroxide at the sametemperature until precipitation is complete. Wash the precipitate bydecantation with distilled water, collect on a filter and dry at C.

Example 4.If the solution for treating the pumice, as in Example 1,comprises 50 parts of nickel nitrate, 2.6 parts of cerium nitrate and7.5 parts of aluminum nitrate in 70 parts of distilled water, asatisfactory nickel-ceria-alu mina catalyst will be produced.

Example 5.--The pumice is prepared and treated as in Example 1, thesolution for that purpose being made by dissolving 50 parts of nickelnitrate and 5 parts of chromium nitrate in 70 parts of distilled water.

Example 6.A nickel chromate catalyst can be prepared by dissolving 70parts of nickel nitrate free from sulphate and chloride in 1000 parts ofdistilled water. Add this solution withstirring to a boiling solution of55 parts of potassium chromate in 1000 parts of distilled water Wash theresulting precipitate until free from nitrates by decantation with colddistilled water. Collect on a filter, knead well and dry for 24 hours atC. and for 4 hours at C. Break up the resulting cake and screen to thedesired size.

The conversion of the hydrocarbons with steam as described in Example 1can be carried out in any suitable form of apparatus which is adapted tosupport the catalyst and to permit the heating thereof during thepassage of the gaseous mixture. The heating is essential because thereaction is endothermic and will not maintain itself, therefore, unlessa suitable quantity of heat .is supplied. While electric heating issuggested, the catalyst chamber can be heated otherwise and the heatshould be conserved, of course, by the provision of suitable heatinterchangers to permit the transfer of heat from the outgoing productto the entering gaseous mixture.

No explanation or theory is ofiered as to what changes in physical formor chemical composition may occur in the catalyst in the course of thereduction treatment with hydrogen or during the conversion ofhydrocarbons with steam. The term catalyst as employed in the claims isintended, therefore, to include the contact mass as prepared as well asany modified form in which it may'exist during the reaction.

While the invention will find its widest application doubtless in theconversion of methane since that hydrocarbon occurs most commonly amongthe compounds which are available for this purpose, it may be'usefui,nevertheless, in converting the higher homologues of methane, (ethane,propane, etc), because these react even out departing from the inventionor sacrificingany of the advantages thereof.

I claim:

1. The process of manufacturing hydrogen which comprises passinga'gaseous mixture of steam and a hydrocarbon over a heated catalyticbody containing nickel and an oxide of one of .the elements selectedfrom the group consisting of boron and yttrium at a temperature below700 C.

2. The process of manufacturing hydrogen which comprises passing agaseous mixture of steam and methane over a heated catalytic bodycontaining nickel and an oxide of one of the elements selected from thegroup consisting of boron and yttrium at a temperature below 700 C.

ROGER WILLIAMS.

